The present invention relates to an electronic fuel feeder for feeding, into a suction tube of an internal combustion engine, an amount of a fuel corresponding to an air flow rate signal generated by a suction air flow meter provided in the suction pipe. In particular, it relates to an electronic control apparatus for operating an optimum fuel flow rate corresponding to the air flow rate.
Heretofore, such an electronic fuel injection device has been formed of an analogue control system. For example, an air flow meter for measuring the suction air flow rate is an analogue type meter for continuously varying an output voltage corresponding to the suction air flow rate. An analogue electronic circuit (computer) for receiving the output signal then has been used to operate the air flow rate signals and to perform analogue operations on the other analogue input signals for calibration (for example, voltage for coolant temperature or voltage for suction air temperature), thereby deciding the optimum fuel flow rate.
In the electronic circuit having said structure, a fault of an electronic part causes an error in the fuel flow rate. Therefore, remarkably high reliabilities of the electronic parts have been required. Recently, integrated electronic circuits have been remarkably developed. LSI (large scale integrated circuit) has been used in such a fuel control electronic device and the remarkably high reliability of LSI has been required because LSI is used for the important control functions.
Thus, it is difficult to completely eliminate a fault, even if highly reliable LSI is used. It is necessary to provide certain back-up means for overcoming a fault. In the above-mentioned analogue electronic control system, redundant circuits having the same structure have been provided, thereby requiring a remarkably large size of the circuit.